1. Field of the Invention
This invention relates generally to the area of watering devices for use in gardening and, more specifically, to automatic irrigation devices known as hygrostats, which include a valve and an expansible member designed to sense the moisture content of soil and to activate and deactivate the watering system accordingly.
2. Description of the Prior Art
Irrigation systems are normally designed to irrigate for a predetermined period and at regular intervals. However, such systems are unresponsive to variables which affect the moisture level in a given area of soil. Such variables include rainfall and higher or lower humidity levels, as well as rate of absorption by plants. As a result, most irrigation systems either overwater or underwater the soil, depending on weather variations, etc. To alleviate the problems of over- or underwatering, individual inventors have directed their efforts toward devices known as hygrostats or moisture-sensitive valves which sense the moisture level of the soil in a given area and allow water to pass therethrough whenever the moisture content falls below a given level. While some effort has been directed toward electrically monitoring the moisture level in the soil and actuating a valve electronically, the present invention is more directed toward moisture-responsive actuators which are mechanical in nature. Such mechanically actuated moisture-responsive actuators generally employ a moisture-sensitive element to open and close the valve. One such moisture-responsive element, wood, is well known and often used. With an increase in the moisture level in soil, the moisture-responsive element expands to shut off a valve, and with a decrease in the moisture level in the soil, it contracts, allowing watering. None of the prior art of which applicant is aware has taught a moisture-responsive actuator having the unique features and being of the unique construction of the present invention.